So, I’m following the ‘Be Iron Fit Competitive plan’ for my first Ironman which will be IMUK2014. This will be the first time I’ve followed a structured training plan…however I have been training regular in all 3 disciplines most weeks (3x sessions in total) for the last 8m.

I know there a great deal of threads on heart rate zone calculations on the forums, which I’ve been part of in the past, however I’m having difficulty getting my head specifically around Fink’s Zone 2.

I’m sure you all know he basis zones on Max HR (to which I’ve field tested myself and not used a formula). He states zone 2 as being 75-85% of MaxHR which contradicts almost all the literature I’ve read around aerobic training %ages based on HRMax. It almost seems to me that his zone 1 % (65-75) is more what I’d expect from an aerobic training zone, but then what would be recovery?

My worry is that by following the Zone 2 sessions (which is the majority of the time) I’m going to end up overtraining and not building my aerobic base sufficiently (as I gather is essential in the early base stage of IM training) and as such spending more time anaerobically and not burning enough of my fat stores. I’m trying to use RPE on both the bike and run, and I’m probably over thinking it all, but I wondered if anyone else has found the same thing when using these plans? I did some reading on the Maffetone 180 formula and wondered if I should maybe just follow that for the base weeks?

On a slightly different line, I’m also finding it hard to hold a zone on the bike, my heart rate is up and down all the time between Z1&2. Is this common in the early days of IM training and will it improve i.e. start to find it easier to hold say zone 2 all the time?

I have used the Maffetone Method since a few months after beginning tri training. I gave the "Be Iron Fit" calculation a whirl. I just felt I was training harder but not seeing any gains in any other areas. So, I went back to MAF for the remainder of the BIF plan....

I've completed IMUK 2012&2013 and have entered for 2014. It is a fantastic event and the support on the day is amazing!

As for heart zones that does seem a bit high (higher than mine anyway). The most successful method I have used (I've used most) has been to test yourself first and work out your Lactate Threshold (LT). This can be done by;

- Bike: warm up for 10-15 mins, then cycle as fast as you can maintain for 30mins. Once complete take your average heart rate for the last 20 mins. This is your Bike LT.
- Run: warm up for 10-15 mins, then run as fast you can maintain for 20 mins. Record your average heart rate for the last 10 mins. This is your run LT.

@Andrew: I must admit I'm a bit like a kid in a sweet shop at the moment. I live in Adlington, which you'll know is on the bike course, so have watched for the last 4 years. Chuffed to bits I managed to secure a spot this time round and cant wait for July, although having said that I'm sure as time creeps up that might turn to nerves!

I did do a LT field test about 8 months ago (run only) and that yielded a threshold of 186; when I dropped the numbers into the BT zone calculator Z2 came back with 159-169. This just felt way too high, I was struggling to stay in that range as I was working pretty hard (or harder from an RPE standpoint). Clearly your % differs and the zone they they would equate to is more like where I "feel" Z2 should be, what made you decide on that Z2 %?

I kind of decided to bin off using the LT zones and was just training by RPE, however after deciding on the Iron Fit programme for the IM thought it made sense to use Fink's suggested zones. I knew my Max for bike & run so just worked the zones out based on was he recommends. It just seemed to me that Z2 was rather high in terms of % of Max.

For the first 3 weeks of the plan, the majority asks for Z2 sessions, and I've kind of kept to the top end of Z1 in the main for everything, which so happens so be ~148bpm (pretty much bang on MAF). Think I'm going to stick with it for the next 7 weeks and see how I feel moving into the build phase......

I have been following the Joe Friel triathlon bible method of calculating HR zones but the ones above are from the Tri-Ripped training plan I am following. I prepare these for the exact reason you said; they 'feel' right.

I would say you are doing the right thing and continuing until you retest for the next phase.

Good luck with you training. I live local too in Golborne. IMUK is an awesome day. I'm keen to get my training in now so I can 'enjoy' the day a bit more this time.